1. Field of the Invention
The invention relates generally to plumbing devices, including valves and conduits, and to pressure measurement equipment. The invention relates particularly to apparatus configured as an assembly to monitor intra-abdominal pressure of a medical patient.
2. State of the Art
It has been determined that the intra-abdominal pressure of a medical patient can be used as a diagnostic tool to assess progress of the patient's recovery subsequent to a medical procedure. For example, the intra-abdominal pressure of the patient can be expected to increase subsequent to a surgical procedure due to fluid leakage and edema in the abdominal cavity. By monitoring the patient's intra-abdominal pressure, a practitioner may receive advance warning of complications resulting from the surgical procedure. In such case, the practitioner may be better prepared to take adequate counter-measures before the patient displays perceptible outward signs of distress and before a life-threatening situation may develop.
Currently employed techniques used to monitor a patient's intra-abdominal pressure are adapted to measure the pressure of fluid contained within the patient's bladder at intervals spaced apart in time. While the pressure reading at a pressure transducer may not correspond to the actual value of intra-abdominal pressure, trends in measured pressure will correlate to trends in intra abdominal intra-abdominal pressure in the patient.
One way to measure a patient's intra-abdominal pressure involves disassembling a urinary catheter drain tube to inject saline through the catheter and into the patient's bladder. (For convenience, a urinary catheter will generally be referred to in this disclosure as a Foley catheter, due to its common use). Unfortunately, opening the closed drainage system plumbing places both the patient and the health care practitioner at increased risk of infection. It is possible to use a three-way Foley catheter, but such catheters are more expensive and are not routinely used. Use of a three-way Foley catheter would require either pre-knowledge of its necessity or replacement of a standard catheter. The former option increases costs and the latter would increase both costs and risk of patient infection.
A different approach for introducing a bolus of fluid into a patient's bladder incorporates the aspiration port included in a urinary catheter drain system as a fluid injection port. The drain tube connected to the Foley catheter is blocked, and the needle of a syringe is passed through the catheter's aspiration port to permit injection of a saline bolus. After the injection needle is removed, a needle for a manometer or pressure transducer is then inserted through the aspiration port to record bladder pressure. Undesirably, approaches involving use of needles, particularly in the vicinity of the patient's legs, to assemble the pressure measuring apparatus place both the patient and the health care practitioner at risk of needle sticks.
With reference to FIG. 1, a currently preferred arrangement adapted to monitor a medical patient's intra-abdominal pressure is generally indicated at 100. A patient is fitted with a urinary catheter 102, such as a Foley catheter. A fluid source, such as saline bag 104, is connected in fluid communication to the catheter 102 upstream of an occluding device 108 temporarily applied to block the catheter drain conduit 106. Interruption of the urine drain path from the patient generally is permitted only temporarily as required to effect pressure measurements.
The device 100 includes a pair of two-way or three-way stopcocks, 110 and 112, respectively. One end of fluid supply tube 114 is connected to a one liter saline bag 104. The other end of fluid supply tube 114 is connected to an inlet port of stopcock 110. A valve stem in stopcock 10 may be oriented to permit fluid to flow from bag 104 toward syringe 116. When syringe 16 is full, or charged with fluid as desired, the valve stem of stopcock 110 is adjusted by way of a manual rotation to permit fluid flow from the syringe toward stopcock 112 while resisting fluid flow toward bag 104. Stopcock 112 can be adjusted to direct a bolus of fluid from syringe 116 for flow through tubing 120 towards catheter 102. Stopcock 112 may also be adjusted to an alternate configuration to provide fluid communication between a pressure measuring device 121 and tubing 120 while resisting fluid flow toward stopcock 110. An infusion needle or angiocatheter 122 carried at an end of tubing 120 is inserted into urine collection port 125 to couple the tube 120 in fluid communication with the catheter 102.
The steps typically required to measure a patient's intra-abdominal pressure, using the arrangement of FIG. 1, are as follows: First the apparatus 100 is assembled, including inserting the needle of an angiocatheter 122 into aspiration port 125 connected to a Foley catheter 102 installed in a patient. Stopcock 110 is oriented to permit fluid flow between bag 104 and syringe 116, and the syringe is filled with saline. Stopcocks 110 and 112 are then both adjusted for fluid flow from the syringe 116 toward the catheter 102. Tube 120 is flushed and filled with saline. Then tubing 106 is occluded to resist fluid flow in a drain direction from catheter 102. Typically, stopcock 112 is then adjusted to resist fluid flow toward syringe 116 and stopcock 110 is configured to permit fluid flow between bag 104 and syringe 116 so that the syringe 116 can be refilled with saline. After priming syringe 116, stopcocks 110 and 112 are adjusted for fluid flow between syringe 116 and catheter 102, whereby to introduce a bolus of fluid into the patient's bladder. Then, stopcock 112 is oriented to provide fluid communication between conduit 120 and pressure transducer 121 while resisting fluid flow toward stopcock 110. Pressure apparatus 121 then indicates the current pressure in the patient's bladder, which may be correlated to intra-abdominal pressure. Subsequent to making and recording the pressure measurement, the occlusion of drain 106 is removed to permit draining the bolus of fluid from the patient's bladder. Such procedure is repeated at intervals spaced apart in time to record trends in the patient's intra-abdominal pressure. The bolus of injected fluid desirably is less than about 100 mL and of uniform size during each successive pressure measurement to avoid effect from bladder wall musculature.
Occluding device 108 may be a clamp or hemostat as illustrated, or sometimes may be a valve. However, operable medical grade valves that are commercially available, such as two-way or three-way stopcocks 110 and 112, typically introduce undesired complications. One complication is that the available medical grade stopcocks typically provide drainage passageways that are too small in diameter for use in a urinary catheter drain. Clogging of the drain bore would be a serious problem.
The location of a catheter drain-occluding valve for a pressure measurement system desirably is in close proximity to the catheter 102—therefore between the patient's legs. Another complication substantially precluding direct inclusion of available medical grade two-way or three-way valves or stopcocks is that such devices route fluid conduits in orthogonal directions at the valve connection locations, thereby creating protruding and invasive plumbing that is uncomfortable to the patient. Furthermore, currently available valves and stopcocks also have protrusions (such as valve actuators or handles), and sharp corners or abrupt changes in shape, that place a patient at risk of injury should such protrusion or corner be impressed into a patient's skin.
The procedures for measuring trends in a patient's intra-abdominal pressure described above undesirably place a patient at risk of infection, or require tiresome manual adjustment of a plurality of plumbing devices, such as two-way valves or stopcocks. It would be a desirable improvement over the prior art to provide a device for measuring trends in a patient's intra-abdominal pressure that is faster and more simple to operate. It would be a further advance over the prior art to eliminate operations requiring needles to assemble or use the pressure measurement apparatus. A still further advance in the art would be to enhance the patient's comfort and increase the patient's protection from injury by minimizing or avoiding contact between the patient and uncomfortable or even harmful medical apparatus.